Pressure gauge

ABSTRACT

A pressure gauge comprises a housing, a main chamber in the housing partly filled with a liquid and a body floating in the liquid. A portion of the body extends through an opening in the housing. A fluid to be measured is introduced into the chamber above the liquid and its pressure is exerted on the surface of the liquid thus causing the body to assume a floated position. A scale is provided outside the housing and the position of the body, and thus the pressure in the measuring chamber, is indicated by the position of the body portion relative to the scale.

United States Patent Lilljeforss [451 Aug. 15, 1972 PRESSURE GAUGE1,950,241 3/ 1934 Hodgson et al ..73/403 72 Inventor: LennartLillieforss i i 7 3,212,195 lO/l965 Paarma et a1 ..33/209 Sweden YPrimary Examiner-Donald O. Woodie] [73] Assignee: AGA Aktiebolag,Lidmgo, Sweden An'omey Larson Taylor and Hinds [22] Filed: March 23,1970 [21] Appl. No.: 21,706 [57] ABS CT A pressure gauge comprises ahousing, a main chamber in the housing partly filled with a liquid and a[30] Forms Application Pmmty Data body floating in the liquid. A portionof the body ex- April 1, 1969 Sweden ..4582/69 t ds th ugh an opening inthe housing. A fluid to be measured is introduced into the chamber abovethe U-S- r t and pressure is exerted on the urface of the [51 Int. Cl...G0ll 7/22 liquid thus causing h body to assume a floated posi [58]FiEld 0 Search 393 tion- A scale i p i outside the h i g and theposition of the body, and thus the pressure in the mea- [56] ReferencesCned suring chamber, is indicated by the position of the UNITED STATESPATENTS body portion relative to the scale.

1,945,042 1/1934 Ingram ..73/403 14 Claims, 8 Drawing Figures Emil 2Sheets-Sheet 1 71 3Q V/Z g i E 27 Z42? Q Patented Aug. 15, 1972 INYENTORV GUSTAF LENNART LILLJEFORSS BY ATTORNEY- 1 PRESSURE GAUGE BACKGROUND OFTHE INVENTION.

The present invention relates to an instrument for the measuring ofpressure. Instruments of this type usually consist of a housing with ameasuring chamber to which the medium is introduced whose pressure is tobe measured. In the measuring chamber a body is provided to indicate thepressure against a scale.

Known devices of this type have many disadvantages which make theinstrument unsuitable for industrial use. For example, the housing hasto be made of a transparent material to allow the body inside thechamber to be visible. Transparent material such as glass often cannotwithstand the high pressure which may occur in industrial operation.Another disadvantage is the relatively large size which such aninstrument must have.

For the measurement, for example, of the residual amount of gas in emptyacetylene cylinders, the following demands are made on the pressuregauge:

1. it must present good measuring accuracy at low pressure (0.8-atmospheres) 2. it must stand a pressure which is about one hundredtimes as high (i.e. about 337 atmospheres, the pressure which ariseswhen acetylene at a pressure of 31 atmospheres is split into carbon andhydrogen) 3. it must not contain alloys with silver or with coppercontent over 65 percent 3. it must not contain alloys with silver orwith copper 4. it must not consist of glass or other transparentmaterial of imperfect strength and 5. it must be sturdy but notnecessarily portable, have small dimensions and be cheap to manufacture.

BRIEF SUMMARY OF THE PRESENT INVENTION In accordance with the presentinvention, the abovementioned requirements have been met and aninstrument of good measuring accuracy has been obtained.

Moreover, the instrument gives a linear indication and the reading canbe carried out ona linear scale.

The instrument in accordance with the invention is characterized in thatthe movable body is bar-shaped and that it projects from the measuringchamber through an opening. At the opposite end the movable body has acounter-weight. By optionally providing the instrument with compensationchambers which can be connected to the measuring chamber, it becomespossi ble to correct the instrument for the measurement of the pressureof. fluids at, for example, different temperatures of different pressureranges.

The instrument according to the invention comprises a housing, a mainchamber in said housing partly filled with a liquid, means defining anopening in the wall of said measuring chamber above the level of saidliquid, a rigid body floating in said body and extending upwardlythrough said opening, said body being freely moveable in said openingupon motion of said body due to changes in the liquid level in saidmeasuring chamber, conduit means to introduce afluid the pressure ofwhich is to be measured into said measuring chamber above said liquidlevel, and means for indicating the distance moved by the portion ofsaid body extending outside of said measuring chamber in response tofluid pressure above said liquid level.

DETAILED DESCRIPTION A preferred embodiment of the instrument inaccordance with the invention is shown in the enclosed drawings,wherein:

FIG. I is a longitudinal cross-section view through an instrumentaccording to the invention;

FIG. 2 is a longitudinal sectional view of a modified embodiment of theinstrument in accordance with FIG.

FIG. 3 is a section view along the line A-A of FIG.

FIG. 4 is a detail section view of an embodiment of a change-overarrangement alternative to that shown in FIG. 2;

FIG. 5 is a longitudinal cross section view of an alternative instrumentaccording to the invention;

FIG. 6 shows a simple embodiment fot the correction of the instrumentscale readings;

FIGS. 7 and 8 show alternative embodiments of the seal of the opening ofthe chamber.

In FIG. 1 is shown the housing 1 of the instrument with a tubularmeasuring chamber 2, which 'has an opening 3 through the housing wall.This opening is adapted to a bar-shaped body 4 which projects throughthe opening and has a first end 5 constituting an indicator for readingagainst a linear scale 6. At the other end of the body 4 acounter-weight 7 is accomodated. The counter-weight 7 is partly immersedin a liquid 8 present in the measuring chamber 2, which may preferablybe mercury or some other heavy liquid. An inlet tube 9 serves tointroduce the medium whose pressure is to be measured into the measuringchamber. A wheel 10 witha plunger 11 is provided for adjustment of thezero point of the instrument by adjustment of the liquid level in themeasuring chamber 2. On top of the liquid 8 a layer of a protectiveliquid 12 may be placed so that the medium whose pressure is to bemeasured cannot come into contact with the liquid 7.

The device is utilized to measure pressure in the following manner. Thezero position of indicator 5 is adjusted by manipulation of wheel 10 asnecessary. The

fluid to be tested, such as acetylene gas, is introduced into themeasuring chamber 2 through conduit 9. The gas pressure above the liquidforces the floating body to rise a distance linearly proportional to theincrease in the pressure in chamber 2. Scale 6 is convenientlycalibrated to read pressure directly. In a preferred embodiment, thetubular measuring chamber 2 is provided in a portion 13 whichcorresponds to the section where the liquid level moves during use ofthe instrument, with well finished walls. Thus, accurate measuringvalues can be obtained without excessive accuracy having to be devotedto the manufacture of the remaining walls of the measuring chamber 2.

It will be readily apparent that the useful range of the device will belimited by the distance which the floating body can move. Accordingly,in a preferred embodiment, the device includes means to alter thesurface area of the liquidsupporting the float to alter the distancethat the body moves in response to a given fluid pressure in themeasuring chamber. When the surface is large, a given pressure willcause a relatively large motion of the body. Correspondingly, when thearea is reduced, the same pressure above the liquid with cause arelatively small motion of the body.

For some measurements, such as the measurement of acetylene gaspressure, the primary purpose is to determine the amount of materialpresent. In this event, it is necessary to compensate for variations inthe gas temperature. According to the invention, this is readilyaccomplished by utilizing the above-mentioned means for altering thesurface area of the liquid in the measuring chamber. Thus, when a hotgas is introduced, the liquid surface area is reduced an amountcorresponding to the extra pressure occasioned by the elevatedtemperature. In an alternative arrangement, temperature compensation canbe accomodated by a set of scales moveable into alignment with the bodyportion extending outside the housing.

For the compensation of, for example, variations of temperature, theinstrument can be provided with a number of compensation chambers 14which are shown in the FIGS. 2-4. These are connected to the upper andto the lower parts of the measuring chamber 2. The lower connectingpoint is regulatable by means of a change-over device. The change-overdevice of FIG. 2 comprises a wheel 15 placed at the base of the housing1 and a disc 16 arranged on the same axle as the wheel 15. In the uppersurface of the disc 16 is a recess 17 which comprises the centralportion and a sector of the disc. The lower end of measuring chamber 2is located just above the central portion of the said disc 16 and thelower ends of compensating chamber 14 are located just above the edge ofthe disc 16. By twisting of the disc 16 one or more of the compensatingchambers 14 can be connected to the measuring chamber 2 via the recess17. The wheel 15 may be provided with a scale 18, which indicates thedegree of temperature compensation that has been set.

FIG. 4 shows an alternative change-over device. The sealing of thecompensation chambers 14 takes place in this embodiment by means of thevalve bodies 23 present in each, which normally float and keep thecompensation chamber open, but which on twisting of the annular wheel24, which contains one or more magnets 25, are forced down and close thecompensating chambers 14. The housing is provided in this embodimentappropriately with magnetically conducting bushings 26 which increasethe magnetic force and give better selectivity for the effect on thevalve bodies 23.

In FIG. is shown in instrument with compensation chambers of a somewhatdifferent type. The compensation chambers are provided here with twowedges 27 and 28 which are displaceable in relation to one another. Theycan be actuated by the gearwheel 29 on the axle of a wheel 30 and allowcontinuous compensation without the zero adjustment being affected. Thesize and shape of the wedges 27 and 28 are selected such that a changeinduced in the compensation chamber volume by motion of one wedge in afirst direction to change the surface area of the liquid therein iscompensated for by motion of the other wedge in the other direction.Thus, the surface area is continuously alterable without changing theliquid level.

FIG. 6 shows another and very simple method for the compensation of theinstrument. By lateral displacement of the scale 31 whose scale-linesare arranged in a fan shape, the scale can be adjusted in relation tothe bar shaped body 4 for different degrees of compensation.

The measuring with the instrument is simple and requires few movementsonce the instrument has been adjusted to zero. The compensation can takeplace without the zero adjustment being affected. Before the start ofthe measurement the correct degree of compensation is set. Then themedium whose pressure is to be measured is fed to the measuring chamber2 and any compensation chambers which may be connected. On putting themeasuring chamber under pressure, a certain leakage will occur throughthe opening 3. This leakage is preferably very small however, since theopening is well fitted to the bar shaped portion of the float body.

As can be seen from FIGS. 7 and 8 the opening 3 can be sealed by fillingthe gap between the housing 1 and the bar 4 with a wetting liquid seal21 (FIG. 7) or by filling an annular groove in the wall of the housing 1with a non-wetting liquid 22 (FIG. 8).

At certain measuring operations where very good accuracy of themeasuring result is desirable, a certain leakage may be an advantage.Due to the turbulence which occurs at the opening 3, the bar shaped body4 with the counter-weight 7 is induced to vibrate so that these partsare not retained together by surface tension forces and friction. Tofurther reduce friction, the opening through which the bar shaped bodyprojects can be formed by a hollow edge with an acute angle so as toprevent the settling of dust particles in the open- The instrument isintended for a certain limited measuring range, but should the .pressureof the medium introduced exceed the highest pressure specified withinthe measuring range, the instrument will be able to withstand this too.By shaping the opening 3 as a valve seat, a sealing ring 32 fitted tothe top of the counterweight 7 can seal the opening 3, should themeasuring deflection be maximum. In a corresponding manner, the outerend of the bar 4 may be provided with a sealing ring 33, so that theopening 3 is sealed if the pressure in the chamber 2 gets below acertain value. The sealing rings 32 and 33 can, of course, also befitted in the housing 1 instead.

The range of application mentioned above, namely the measurement of theresidual gas in empty acetylene gas cylinders, constitutes only oneexample of the spheres of application for which the instrument inaccordance with the present invention is suitable. The instrument is ofcourse applicable in any industrial pressure measurement.

What is claimed is:

1. An instrument for measuring pressure comprising: a housing; ameasuring chamber in said housing partly filled with a liquid; meansdefining an opening in the wall of said measuring chamber above thelevel of said liquid; an elongated rigid body floating vertically insaid liquid and extending upwardly through said opening with asubstantial portion thereof submerged in the liquid, sealing means inthe opening surrounding said body, said body being freely moveablelongitudinally in said opening; conduit means to introduce a fluid thepressure of which is to be measured into said measuring chamber abovesaid liquid level and about a portion of the body extending above theliquid level whereby said body moves longitudinally in said opening inresponse to pressure in the measuring chamber above said liquid levelrelative to pressure outside of said opening in said housing wall; andmeans for indicating a distance moved by the portion of saidbodyextending outside of said measuring chamber in response to fluidpressure in said measuring chamber above said liquid level the effectiveweight of said body increasing at higher pressure within said housing asthe body rises relative to the level of liquid in said chamber.

2. An instrument according to claim 1 wherein said measuring chamberincludes a portion having accurately machined walls, said liquid levelbeing located adjacent said accurately machined walls.

3. An instrument according to claim 1 including means for altering thesurface area of the liquid supporting said body in said measuringchamber.

4. An instrument according to claim 3 wherein said surface area alteringmeans comprises at least one compensating chamber containing liquid atsubstantially the same level as the liquid level in said measuringchamber, and means for interconnecting said measuring chamber and saidcompensating chamber at points above and below the liquid level to alterthe surface of the liquid in which said body floats.

5. An instrument according to claim 4 including a plurality ofcompensating chambers and means for connecting one or more of saidcompensating chambers with said measuring chamber.

6. An instrument according to claim 5 wherein said connecting meanscomprises a revolving body including an eccentric recess moveable intoadjacency with the lower end of each compensating chamber to provide afluid interconnection between the measuring chamber and eachcompensating chamber.

7. An instrument according to claim 5 wherein said connecting meanscomprises a rotating body including at least one magnet operable toactuate valve means interconnecting said measuring chamber and eachcompensating chamber.

8. An instrument according to claim 3 wherein said altering meanscomprises a constant volume, variable surface area compensating chamberand wherein said instrument includes means to vary the surface area ofsaid compensating chamber.

9. An instrument according to claim 8 wherein said compensating chambercomprises two wedge-shaped wall elements each moveable relative to oneanother and having a size and shape such that a change induced in thechamber volume by motion of one element in a first direction to changethe surface area of liquid in the compensating chamber is compensatedfor by motion of the other element in the opposite direction.

10. An instrument according to claim 1 wherein said body is providedwith means for sealing said opening when pressure in the measuringchamber is above or below the measuring range of the instrument.

1]. An instrument according to claim 1 including sealing means forsealing the gap between the body and said opening.

12. An instrument according to claim 1 wherein said liquid is protectedfrom said fluid being measured by a layer of a second liquid on thesurface of said liquid.

13. An instrument according to claim 1 wherein said indicating meanscomprises a scale adjacent the portion of said body extending throughsaid opening out side said housing.

14. An instrument according to claim 13 wherein said scale is laterallydisplaceable with respect to said body portion.

1. An instrument for measuring pressure comprising: a housing; ameasuring chamber in said housing partly filled with a liquid; meansdefining an opening in the wall of said measuring chamber above thelevel of said liquid; an elongated rigid body floating vertically insaid liquid and extending upwardly through said opening with asubstantial portion thereof submerged in the liquid, sealing means inthe opening surrounding said body, said body being freely moveablelongitudinally in said opening; conduit means to introduce a fluid thepressure of which is to be measured into said measuring chamber abovesaid liquid level and about a portion of the body extending above theliquid level whereby said body moves longitudinally in said opening inresponse to pressure in the measuring chamber above said liquid levelrelative to pressure outside of said opening in said housing wall; andmeans for indicating a distance moved by the portion of said bodyextending outside of said measuring chamber in response to fluidpressure in said measuring chamber above said liquid level the effectiveweight of said body increasing at higher pressure within said housing asthe body rises relative to the level of liquid in said chamber.
 2. Aninstrument according to claim 1 wherein said measuring chamber includesa portion having accurately machined walls, said liquid level beinglocated adjacent said accurately machined walls.
 3. An instrumentaccording to claim 1 including means for altering the surface area ofthe liquid supporting said body in said measuring chamber.
 4. Aninstrument according to claim 3 wherein said surface area altering meanscomprises at least one compensating chamber containing liquid atsubstantially the same level as the liquid level in said measuringchamber, and means for interconnecting said measuring chamber and saidcompensating chamber at points above and below the liquid level to alterthe surface of the liquid in which said body floats.
 5. An instrumentaccording to claim 4 including a plurality of compensating chambers andmeans for connecting one or more of said compensating chambers with saidmeasuring chamber.
 6. An instrument according to claim 5 wherein saidconnecting means comprises a revolving body including an eccentricrecess moveable into adjacency with the lower end of each compensatingchamber to provide a fluid interconnection between the measuring chamberand each compensating chamber.
 7. An instrument according to claim 5wherein said connecting means comprises a rotating body including atleast one magnet operable to actuate valve means interconnecting saidmeasuring chamber and each compensating chamber.
 8. An instrumentaccording to claim 3 wherein said altering means comprises a constantvolume, variable surface area compensating chamber and wherein saidinstrument includes means to vary the surface area of said compensatingchamber.
 9. An instrument according to claim 8 wherein said compensatingchamber comprises two wedge-shaped wall elements each moveable relativeto one another and having a size and shape such that a change induced inthe chamber volume by motion of one element in a first direction tochange the surface area of liquid in the compensating chamber iscompensated for by motion of the other element in the oppositedirection.
 10. An instrument according to claim 1 wherein said body isprovided with means for sealing said opening when pressure in themeasuring chamber is above or below the measuring range of theinstrument.
 11. An instrument according to claim 1 including sealingmeans for sealing the gap between the body and said opening.
 12. Aninstrument according to claim 1 wherein said liquid is protected fromsaid fluid being measured by a layer of a second liquid on the surfaceof said liquid.
 13. An instrument according to claim 1 wherein saidindicating means comprises a scale adjacent the portion of said bodyextending through said opening outside said housing.
 14. An instrumentaccording to claim 13 wherein said scale is laterally displaceable withrespect to said body portion.